How is it good for my client to spend 30% more to acquire a customer? Google champions the fact that their ads produce more $ for them (than comparable products from Y!/MS), which is good only for them and their shareholders. I don't see how the product matters in this regard. It's all about ROI and unless these Goog customers are more apt to buy again and again it's not worth it.
That's why I wanted more details. It's implausible to me that so many people would choose Google over Yahoo if Google delivered worse results for more money. I'd also be confounded at Google's ability to do so while hiring so many smart people. Perhaps Google delivers more purchases per click, or more repeat customers (they are worth something, aren't they?). Perhaps Yahoo is particularly good at certain kinds of clients (that's why I asked).
I could see people choosing the Goog for the sheer numbers. There's simply more inventory (impressions). But with clients who have a budget and therefore aren't maxing the inventory, this advantage is lessened.
That's bad for advertisers, and good for Google. Yahoo! remains a better advertising vehicle for my clients, with 20-30% less CAC.